Comprehensive analysis of Arabidopsis expression level polymorphisms with simple inheritance

In Arabidopsis thaliana, gene expression level polymorphisms (ELPs) between natural accessions that exhibit simple, single locus inheritance are promising quantitative trait locus (QTL) candidates to explain phenotypic variability. It is assumed that such ELPs overwhelmingly represent regulatory element polymorphisms. However, comprehensive genome-wide analyses linking expression level, regulatory sequence and gene structure variation are missing, preventing definite verification of this assumption. Here, we analyzed ELPs observed between the Eil-0 and Lc-0 accessions. Compared with non-variable controls, 5′ regulatory sequence variation in the corresponding genes is indeed increased. However, ∼42% of all the ELP genes also carry major transcription unit deletions in one parent as revealed by genome tiling arrays, representing a >4-fold enrichment over controls. Within the subset of ELPs with simple inheritance, this proportion is even higher and deletions are generally more severe. Similar results were obtained from analyses of the Bay-0 and Sha accessions, using alternative technical approaches. Collectively, our results suggest that drastic structural changes are a major cause for ELPs with simple inheritance, corroborating experimentally observed indel preponderance in cloned Arabidopsis QTL

Systematic engineering design approach for improvement of oil-free twin-screw compressors

Twin-screw compressors are widely used in industry, especially in compressed air, refrigeration, air-conditioning and process gas which consume a significant part of the world's energy. Nowadays, oil-injected compressors represent the majority of twin-screw compressors in the market due to their high efficiency and reliability. The oil-free compressor is potentially a better solution in the context of the net-zero CO2 target in 2050. However, due to its high thermal deformation and small clearances, this technology still suffers from reliability issues. To remedy this problem disruptive innovative solutions are required. In this purpose, the present study uses a systematic engineering design process to develop new concepts for the improvement of the oil-free twin-screw compressor. The paper is focused on the first two phases of the design process which are the definition of problem and the conceptual design. In the problem definition, main objectives are expressed and are divided into sub-objectives and weighed using an objective tree decomposition. Moreover, a thorough functional model of the oil-free compressor is detailed with a focus on the leakage paths and heat transfers. For the conceptual design, engineering characteristics extracted from the functional analysis have been assessed against the most important objectives using Quality Function Deployment matrices (QFD). Based on the developed problem definition, new concepts have been generated and three distinct concept categories have been further explored: Secondary flow; Surface features; Clearance control and monitoring. The evaluation, embodiment and detailed designs of the concepts, using experimental and numerical analyses will follow

Analyse expérimentale de l'effet Morton

The main goal of this thesis is the experimental study of the Morton effect in hydrodynamic bearing for rigid and flexible rotors. The Morton effect is a thermally induced increase of the synchronous vibration phenomenon that appears in journal bearing. The introduction part permits to describe the thermal instabilities with firstly a focus on the Newkirk effect and its mathematical description to understand the philosophy of thermal instabilities. Bibliography study of the Morton effect is fully described (case studies, numerical analyses, experimental analyses). The first experimental analysis is conduct for a rigid rotor on a plain journal bearing. In this configuration, the test rig is detailed, the dynamic characteristics of the bearing are experimentally identified and then the tests at constant rotational speed show the “stable” Morton effect. The second study is achieved with a flexible rotor and permits to show the influence of the start-up time on the Morton effect stability. The last experimental study is realized with the flexible rotor on a tilting pad journal bearing with flexible pivot. This bearing being of a particular design, a bibliography allows to understand its principles, its pros and cons and its applications. Its design and its experimental characterization are detailed and then the experimental results show the unbalance influence on stability. To conclude, experimental results are compared and allow a better understanding of the Morton effect in the journal bearing and its influence on the rotordynamic.Cette thèse a pour objectif d’étudier expérimentalement l’effet Morton pour différents types de paliers et un rotor rigide ou flexible. L’effet Morton est un phénomène d’instabilité thermique se produisant dans les paliers hydrodynamiques qui a pour conséquence d’influencer le comportement vibratoire du système rotor-palier. L’introduction permet d’évoquer les différents phénomènes d’instabilité thermique, en se concentrant dans un premier temps sur l’effet Newkirk pour en décrire mathématiquement son fonctionnement et comprendre la philosophie des phénomènes d’instabilité thermique. L’étude bibliographique de l’effet Morton est ensuite détaillée (cas industriels, modélisation numérique et analyse expérimentale). La première analyse expérimentale est réalisée pour un rotor rigide supporté par un palier cylindrique. Avant l’analyse des essais dans cette configuration, le banc d’essais est détaillé, les caractéristiques dynamiques du palier sont identifiées expérimentalement. Les essais réalisés à vitesse constante montrent la présence de l’effet Morton « stable ». La seconde étude est conduite avec un rotor flexible et permet de mettre en évidence l’influence du temps de démarrage sur l’apparition d’un comportement instable. La dernière étude expérimentale est réalisée avec le rotor flexible supporté par un palier à patins oscillants à pivots flexibles. Le palier étant d’une conception particulière, une étude bibliographique permet de comprendre son fonctionnement, ses points forts et ses applications. Sa conception, son dimensionnement et sa caractérisation expérimentale sont ensuite détaillés, puis les résultats expérimentaux montrent l’influence du balourd initial sur la stabilité. Pour finir, les résultats expérimentaux de chaque configuration sont comparés et permettent de mieux appréhender le comportement de l’effet Morton dans les paliers hydrodynamiques et son influence sur la dynamique du rotor

Experimental Analysis on the Morton Effect

Cette thèse a pour objectif d’étudier expérimentalement l’effet Morton pour différents types de paliers et un rotor rigide ou flexible. L’effet Morton est un phénomène d’instabilité thermique se produisant dans les paliers hydrodynamiques qui a pour conséquence d’influencer le comportement vibratoire du système rotor-palier. L’introduction permet d’évoquer les différents phénomènes d’instabilité thermique, en se concentrant dans un premier temps sur l’effet Newkirk pour en décrire mathématiquement son fonctionnement et comprendre la philosophie des phénomènes d’instabilité thermique. L’étude bibliographique de l’effet Morton est ensuite détaillée (cas industriels, modélisation numérique et analyse expérimentale). La première analyse expérimentale est réalisée pour un rotor rigide supporté par un palier cylindrique. Avant l’analyse des essais dans cette configuration, le banc d’essais est détaillé, les caractéristiques dynamiques du palier sont identifiées expérimentalement. Les essais réalisés à vitesse constante montrent la présence de l’effet Morton « stable ». La seconde étude est conduite avec un rotor flexible et permet de mettre en évidence l’influence du temps de démarrage sur l’apparition d’un comportement instable. La dernière étude expérimentale est réalisée avec le rotor flexible supporté par un palier à patins oscillants à pivots flexibles. Le palier étant d’une conception particulière, une étude bibliographique permet de comprendre son fonctionnement, ses points forts et ses applications. Sa conception, son dimensionnement et sa caractérisation expérimentale sont ensuite détaillés, puis les résultats expérimentaux montrent l’influence du balourd initial sur la stabilité. Pour finir, les résultats expérimentaux de chaque configuration sont comparés et permettent de mieux appréhender le comportement de l’effet Morton dans les paliers hydrodynamiques et son influence sur la dynamique du rotor.The main goal of this thesis is the experimental study of the Morton effect in hydrodynamic bearing for rigid and flexible rotors. The Morton effect is a thermally induced increase of the synchronous vibration phenomenon that appears in journal bearing. The introduction part permits to describe the thermal instabilities with firstly a focus on the Newkirk effect and its mathematical description to understand the philosophy of thermal instabilities. Bibliography study of the Morton effect is fully described (case studies, numerical analyses, experimental analyses). The first experimental analysis is conduct for a rigid rotor on a plain journal bearing. In this configuration, the test rig is detailed, the dynamic characteristics of the bearing are experimentally identified and then the tests at constant rotational speed show the “stable” Morton effect. The second study is achieved with a flexible rotor and permits to show the influence of the start-up time on the Morton effect stability. The last experimental study is realized with the flexible rotor on a tilting pad journal bearing with flexible pivot. This bearing being of a particular design, a bibliography allows to understand its principles, its pros and cons and its applications. Its design and its experimental characterization are detailed and then the experimental results show the unbalance influence on stability. To conclude, experimental results are compared and allow a better understanding of the Morton effect in the journal bearing and its influence on the rotordynamic

Flowering as a Condition for Xylem Expansion in Arabidopsis Hypocotyl and Root

International audienc

Study of leakage flow in oil-free positive displacement rotary machines using particle image velocimetry

Rotary positive displacement machines (PDM) are widely used in industry. Oil free PDM's are used in applications where presence of oil is not allowed, but they still are not much utilised due to challenges with reliability and efficiency related to extensive thermal loads. Their efficiency is important to meet carbon footprint targets while increasing reliability will allow their wider use. The main contributor to losses is the internal leakage through clearance gaps between stationary and rotating parts driven by the differential pressure between chambers. Due to the transient nature of leakage flows in running conditions, the measurement of velocity flow field inside the clearance gap is challenging but can provide significant information about flow physics. Thus, understanding of the velocity flow field is essential for developing methods to increase efficiency without compromising reliability. The flow field in clearance gaps can be captured using Particle Image Velocimetry (PIV) for optically accessible flows. The basic PIV system consists of a light source, camera, tracer particles, and analysis algorithms. In this study the Roots blower is used as a representative of the oil-free PDM for which the velocity field is measured inside the radial clearance gap in the running condition using the PIV technique. An extensive testing campaign has been carried out at various speeds and pressure ratios of the machine. PIV measurements were taken inside, upstream, and downstream of the clearance gap. Post-processing of PIV images allows the generation of velocity fields. These pioneering measurements of the velocity field inside the clearance in the machine operating conditions reveal interesting flow physics. Moreover, the large amount of collected experimental data provides an excellent basis for validation of simulation models and further developments

Experimental Identification of Dynamic Coefficients of Fluid Film Bearings by Using Electro-Magnetic Actuator

The present study is focused on the design and use of an ElectroMagnetic Actuator (EMA) for the experimental identification of cylindrical and tilting pad journal bearings rotordynamic coefficients. First, the experimental apparatus is described, then the force-current formulation controlling the EMA is adapted and experimentally validated using the transverse momentum of inertia of the rotor. Finally, an extensive set of experiments is conducted to compute the rotordynamic coefficients of fluid film bearings by resolving a 2 dof syste